Antenna feed system for double polarization

ABSTRACT

Antenna system for double polarization in two high frequency bands of different frequency positions includes a orthomode transducer, in the following text called polarization filter having an antenna end terminal and two directional terminals, one being for right circular polarized waves, and the other being for left circular polarized waves. These directional terminals connect, respectively, with two frequency filters which separate the signals into the lower of the two high frequency bands, and the higher of the two high frequency bands. There are two 3-dB 90° directional couplers, one of which handles right and left circular polarized signals of the lower frequency band, and the other of which handles right and left circular polarized signals of the higher frequency band. The polarization filter is constructed to be phase-symmetrical with respect to its transit paths. The directional terminals of the polarization filter are connected directly to the frequency filters, respectively, or through two structurally symmetrical 45° twisted components of different twisting directions. The connection lines between the frequency filters and the directional couplers in each case for the two frequency bands occupy dual polarization directions of the same frequency range. These are phase-symmetrical pairs of lines with connection elements which match one another in pairs at the same point of the line.

BACKGROUND OF THE INVENTION

The invention relates to an antenna feed system for double polarizationin two high-frequency bands of differing frequency position, consistingof a polarization dividing filter having an antenna-end terminal whichis common to the two frequency bands and having two directional antennaewhich are each assigned to one polarization direction in each case for afrequency dividing filter whose terminal which is common to the twofrequency bands is in each case connected to one of the directionalantennae of the polarization dividing filter, further consisting of afirst 3-dB-directional coupler for the lower frequency band, whosedouble access is connected to a further terminal, assigned to the lowerfrequency band, of the two frequency filters, and further consisting ofa 3-dB-directional coupler for the upper frequency band which isconnected to a further terminal, assigned to the upper frequency band,of the frequency filters.

An antenna feed system of this type is known, for example, from thepublication "Proceedings of Intelsat 5 Earth-Station Technology Seminar"in Munich of the 13th to 18th June, 1976, in particular FIG. K-15. FIG.1 is a block circuit diagram of an antenna feed system of this type forcircular double polarization in two frequency ranges. The fundamentalaim of such an arrangement consists in converting two transmitting bandsof like frequency position, for example, from 5.925 GHz to 6.425 GHz andwith powers of up to approximately 10 KW into a transmitting band ofright-circular wave form and a further transmitting band ofleft-circular wave form, and thus to provide that the latter, againdecoupled from one another, are combined in a common main waveguidewhich also conducts two like-frequency receiving bands with a frequencyposition which is displaced relative to the transmitting bands, forexample from 3.7 GHz to 4.2 GHz in right-circular and left-circularpolarized wave form, thus decoupled from one another. These receivingbands are also separated in respect of their right-circular andleft-circular polarization and, having been converted into the H₀₁ waveform, must be fed to two receiving waveguides.

These functions are fulfilled by the circuit illustrated in FIG. 1 inthe following manner. For example, a 6 GHz band is split by means of a3-dB-directional coupler into two half waves with +90° and -90° phasedifference. The sign of the 90°-phase is dependent only upon which ofthe two arms of the 3-dB-coupler at which feed-in takes place. Thesehalf waves are fed via two identical frequency filters to a polarizationfilter in such a manner that they are at right angles to one another atthe latter's output. If the condition is fulfilled that the two halfwaves travel their path to the polarization filter output without mutualphase distortion, at said output they still possess a mutual time phaseof ±90° and thus represent a purely circularly polarized wave.

The aim of the circuit illustrated in FIG. 1 is, employing one and thesame antenna, to radiate two like-frequency transmitting bandsright-hand circularly and left-hand circularly, thus decoupled from oneanother, and to feed two right-hand circular and left-hand circularwaves received by this antenna in a different frequency band to separatereceiving amplifiers in accordance with their polarization direction.

The difficulties which occur in the realization of the conceptillustrated in FIG. 1 mainly consist in designing the two transit paths,each provided for one frequency band, of the overall arrangement to besymmetrical in construction or at least symmetrical in phase.Furthermore, it is to be endeavored to provide the best possibletransmission properties in respect to attenuation, reflection anddecoupling for the four transit paths of the circuit illustrated in FIG.1.

BRIEF SUMMARY OF THE INVENTION

Therefore, the aim of the present invention is, for an antenna feedsystem of the type described above, to provide a realization, in respectof apparatus, which is characterized on the one hand by compactness ofmechanical construction, and on the other hand, by good transmissionproperties and phase symmetry for all the transit paths of the samefrequency.

Commencing from an antenna feed system for double polarization in twohigh-frequency bands of different frequency position, consisting of apolarization filter having an antenna-end terminal which is common tothe two frequency bands and two directional terminals, each assigned toone polarization direction, each for a frequency filter whose terminalwhich is common to the two frequency bands, is in each case connected toone of the directional antennae of the polarization filter. A first3-dB-directional coupler for the lower frequency band whose double caseis in each case connected to a further terminal, is assigned to thelower frequency band, of the two frequency filters, and furtherconsisting of a 3-dB-directional coupler for the upper frequency bandwhich is in each case connected to a further terminal, assigned to theupper frequency band, of the frequency filters. This aim is realized inaccordance with the invention in that the polarization filter isconstructed to be phase symmetrical in respect to its transit paths. Thedirectional terminals of the polarization filter are connected to thefrequency filters via two 45° stranded components which possessdifferent directions of stranding and are precisely symmetrical withrespect to construction. The connection lines between the frequencyfilters and the 3-dB-directional couplers for two frequency bandsoccupying dual polarization directions of the same frequency range areconstructed as phase-symmetrical line pairs with connection elementswhich match one another in pairs at the same location of the line.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block circuit diagram, which has already beenexplained hereinabove, of an antenna feed system for circular doublepolarization in two frequency ranges,

FIG. 2 illustrates a preferred embodiment in accordance with theinvention of an antenna feed system corresponding to FIG. 1,

FIG. 3 illustrates a further antenna feed system in accordance with theinvention.

FIG. 4 is an enlarged isometric view of the phase symmetricalpolarization filter;

FIG. 5 is a partial sectional view taken along the line V--V of FIG. 4;

FIG. 6 is a sectional view taken along the line VI--VI of FIG. 5; and

FIG. 7 is a view of the structure looking at it in the manner shown bythe line VII--VII of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In order to illustrate the construction of the preferred embodimentshown in FIG. 2, the wide-band polarization filter PW shown in theleft-hand part of FIG. 2 will first be considered. A phase-symmetricalpolarization filter of this type, already disclosed in an earlierproposal, contains a first arm 1 which lies in the longitudinal axis ofthe arrangement and in the exemplary embodiment is of cylindrical designand is provided for connecting an ongoing waveguide of round or squarecross-section, and four sub-arms 2 to 5 which are of identical designand are arranged rotated relative to one another by 90°, and each run atthe same angle relative to the longitudinal axis of the arrangement inthe opposite direction to the first arm. In the exemplary embodiment,these sub-arms of the double branching each have a rectangularcross-section and those pairs of rectangular waveguides which lieopposite one another are of fully symmetrical construction. In thispolarization filter, two sub-arms of the double branching which lieopposite one another are connected in pairs via filter arm sections,which will be explained in detail in the following, to the sub-arms 6 to9 of a series branching SV. A series branching SV of this type consistsof two rectangular waveguides which originally rested one upon anotheron their wide side and which are symmetrically bent away from oneanother at the point at which the partition plate commences. The foursub-arms of the polarization filter are connected in pairs, i.e., thesub-arms which in each case lie opposite one another are connected tothe sub-arms 6 to 9 of the series branchings via filter arm sectionsdesigned as E-displacement components 10, 11 on the one hand, andfurther filter arm sections designed as H-displacement components 12,13, on the other hand. The E-displacement components 10, 11 which areillustrated one above another in FIG. 2 each consist of a rectangularwaveguide component provided on both sides with a waveguide elbow andwhich is bent by the waveguide elbow on both sides in oppositedirections along the wide side. The two E-displacement componets runapproximately in parallel with one another and are commonly alignedobliquely to the longitudinal axis of the arrangement so that their endcross-sections which face towards the sub-arms of the series branchingsare no longer symmetrical to the longitudinal axis of the arrangementbut are displaced by a specific distance relative to the longitudinalaxis. The filter arm sections provided in the other transit path of thepolarization filter are designed as H-displacement components 12, 13 andeach consist of a rectangular waveguide component which is provided onboth sides with a waveguide elbow and is bent by the waveguide elbows onboth sides in opposite directions along the narrow side. Now the tworectangular, access cross-sections of the double branching which lie oneabove another are displaced upwards to such an extent that thecross-sections of the horizontal pair of waveguides are displaceddownwards to such an extent that the displaced cross-sections can becombined in pairs with two identical series branchings which do notmutually penetrate one another. In the above described polarizationfilter, the two transit paths are designed to be phase-symmetrical sothat they enjoy a wide-band phase synchronism. Furthermore, the flangesurfaces lying between the series branchings SV and the rectangularwaveguide accesses are arranged in the same plane. A polarization filterof this kind having two rectangular waveguide accesses with parallelaxes and terminal flange surfaces lying in one plane have a structurallength of approximately 155 mm for a 4/6-GHz design.

As can be seen from FIG. 2, in the construction in accordance with theinvention, the two filter flanges SV (see FIGS. 2, 4 and 5) areconnected without any connection line to a 4/6 GHz frequency filter FWas likewise described in an earlier proposal. A frequency filter FW ofthis kind consists of two waveguide sections 14 (see FIG. 4), 15 ofdiffeent cross-section and the lower frequency band is output coupledvia the extended inner conductor of a radial band stop filter 16, on thewaveguide section which is common to the two frequency bands and, asillustrated in FIG. 2, for high transit power on a third waveguide 17which is coupled to the common waveguide section 14. In the 4/6 HGzdesign, this frequency filter FW has a structural length ofapproximately 75 mm and is provided with a straight 6-GHz-transit andits 6 GHz radial circuit block 16 which is coupled via the lateral 4 GHzresonator 17 in order to provide a possibility of direct connection tothe following pairs of waveguides, aligned in parallel with the mainaxis of the arrangement, of the 6- and the 4-GHz 3-dB-directionalcoupler RK1 and RK2, respectively.

A connection, as described above, of a phase-symmetrical polarizationfilter to two frequency filters identical to one another, represents aphase-symmetrical system filter, for example, for radio relay in the 4-and 6-GHz frequency range, it being possible to operate one and the sameantenna with two linear polarizations decoupled from one another inthese two ranges. For use in satellite broadcasting, an arrangement ofthis kind can also be referred to as an antenna feed system for lineardouble polarization in a transmitting- and receiving-frequency range.

In accordance with the fundamental circuit diagram shown in FIG. 1, aphase-symmetrical system filter of this kind can be extended by anoptimized 3-dB-coupler in each case in the transmitting band and in thereceiving band to form an antenna feed system for circular doublepolarization in these two frequency ranges.

An essential requirement is to establish the shortest possibleconnections from the two coaxial 4-GHz accesses of the frequency filterFW and from its rectangular 6-GHz accesses to the 4- and6-GHz-3-dB-coupler RK2 and RK1, respectively. In order to avoid phasedistortions in the two 4- and 6-GHz branch lines, these connection linesmust also be absolutely phase-symmetrical, i.e., must be electricallyequal in length under all operating frequencies. A phase-symmetrical,double connection of this kind can be achieved by a structurallysymmetrical design of the line pairs, and for this purpose the one linebranch should be constructed as far as possible with the same connectionelements as the other, and these elements should be employed atidentical points of the line. In the exemplary embodiment illustrated inFIG. 2, a structurally symmetrical connection between the two 4 GHzcoaxial accesses of the frequency filters and the pair of waveguides ofthe 4 GHz-3db-coupler to two coaxial waveguide junctions which areidentical to one another, is achieved if, as can be seen from FIG. 2,the waveguide cross-sections of the 4 GHz-3dB-coupler are arranged inL-shape, i.e., if the 3-dB-directional coupler RK2 is designed as a pairof rectangular waveguides arranged in L-shape in respect of thecross-sectional surfaces, and aligned in parallel to the longitudinalaxis of the overall arrangement, in such a way that the narrow side ofthe one waveguide is positioned on the wide side of the other waveguideor possesses a common wall with a part of this wide side. Then couplingopenings K in this common wall serve to couple the magnetic longitudinalfields of the two waveguides to one another.

A corresponding, further L-coupler aligned in parallel with thelongitudinal axis of the arrangement, as illustrated in the lower partof FIG. 2 for the 4-GHz range, is also connected to the rectangular6-GHz-accesses of the frequency filters. As the cross-sections SV ofthese two accesses to the frequency filters lie in the same plane andare also at right angles to one another, although they possess a certaindistance from one another which is inevitably topologically governed bythe construction of the polarization filter, and which is alsoadvantageous for the structurally symmetrical transition to the4-GHz-3db-coupler RK2, as can be seen from FIG. 2, an oblique waveguidesection 15, 15' having a maximum length of λ_(H) is used for connectionto the 6-GHz-3-dB-coupler RK1.

The angles of bend of this 6-GHz double link at which, in both cases orat least in one case, a bend is made simultaneously along the narrow andthe wide side of the waveguide, can be maintained sufficiently small toensure that a phase-symmetrical double transition from the frequencyfilters to the 6-GHz-3db-coupler RK1 can be easily achieved, inparticular since the E-waveguide bend and the H-waveguide bend have avirtually identical phase response with the same angle of bend.

In the case of the "L-coupler" as shown in FIG. 2, the coupling iscarried out similarly to the coupler described for example, in the"Taschenbuch der Hochfrequenztechnik" by Meinke and Gundlach, 2ndEdition, page 433, wherein the rectangular waveguide cross-sections arearranged in T-shape, via the magnetic longitudinal component H_(z),wherein the L-coupler has the advantage that the coupling openings K inaccordance with the illustration in FIG. 2, are arranged in the twowaveguides in the region of the maximum H_(z) components, namely on thenarrow waveguide side of the one waveguide and thus simultaneously inthe edge region of the wide waveguide side of the other waveguide. Thisprovides the advantage that in the L-coupler a smaller number ofcoupling openings is sufficient for a specific coupling attenuation, sothat the L-coupler has a shorter structural length than a correspondingT-coupler.

In order to achieve a stronger coupling per length unit it is expedientto employ the measure, illustrated in FIG. 2, of employing two or aplurality of rows of holes arranged directly beside one another. Toensure that the coupling openings do not lie too far from the positionof the maximum coupling field strength on the narrow waveguide wideside, in the exemplary embodiment shown in FIG. 2, the conventionalround coupling holes have not been provided, but longitudinal holeswhich are displaced relative to one another by approximately half thelength of one hole in the longitudinal direction in two rows directlybeside one another. It is also advantageous that the coupling strengthof a longitudinal hole having a length L which is equal to that of around coupling hole having a diameter D=L. Since in the exemplaryembodiment shown in FIG. 2, the two rows of holes lie very close to thenarrow waveguide side with a maximum H_(z), which furthermore isdistributed in cosine fashion over the waveguide wide side, the two rowsof holes make an approximately equal contribution to the coupling. Itshould be noted that, in order to achieve a high directionalattenuation, the hole spacing in a row of holes must amount toapproximately λ_(H) /4.

In the dimensioning of the coupling openings in the L- and in theT-coupler, it should be ensured that the coupling takes place only viathe H_(z) -component on both sides of the coupling opening, and that dueto the reduction in the H_(z) -component with increasing frequency andconstant power by the factor ##EQU1## the strength of the coupling alsodecreases with increasing frequency. Thus, an increasing couplingattenuation can be measured with an increasing frequency provided thediameters of the coupling openings are smaller than approximately λ_(H)/6. On the other hand, a measurement indicates that even with holeslengths of between λ_(H) /6 and λ_(H) /4 in the upper frequency rangethe coupling strength increases again and the coupling attenuation dropscorrespondingly. This can be explained by the fact that with a hole ofincreasing length, the λ/2 resonance frequency of a coupling holeapproaches the operating frequency range from above and thus the lowerflank of this λ/2 resonance results, in the upper part of the operatingfrequency range, in a drop in the coupling attenuation which increasesin proportion with the frequency. Since, on the other hand, in the lowerpart of the frequency range, the drop in the coupling attenuation causedby the H_(z) rise prevailing at that point is maintained, a couplingattenuation maximum occurs in the middle frequency range. Here themeasured coupling attenuation is virtually constant within a widesubfrequency range. For this reason, a T-coupler, and thus also theallied L-coupler, is at least equivalent to a conventional wide-wallcoupler. A particular advantage of the L-coupler consists in theparticularly non-critical dimensioning of the hole spacing from the walland the resultant increased production tolerance range which is due tothe fact that the coupling is carried out in the cosine-shaped H_(z)maximum.

In the case of the construction shown in FIG. 2, in which the componentsare lined up in the axial direction with very short connection lines, a4/6-GHz-design in which the polarization filter has a structural lengthof 155 mm, acquires an overall structural length of only approximately580 mm and, furthermore, a particularly short extent in the radialdirection.

Based on a mode of functioning which is identical to that in FIG. 2, theexemplary embodiment in FIG. 3 illustrates a further design of theantenna feed system in accordance with the invention, considered frombelow. Providing the arrangement with a perpendicular longitudinal axis,the upper part of the Figure illustrates the same system filter as inthe exemplary embodiment shown in FIG. 2, as a combination of aphase-symmetrical polarization filter PW with two identical frequencyfilters FW. A difference, which is of no electrical significance,consists simply in that in the exemplary embodiment shown in FIG. 3, thefront radial circuit block 16 is not, as in the exemplary embodimentshown in FIG. 2, directly facing the other radial circuit block 16'whose axis points from left to right in the horizontal direction, but isarranged on the opposite wide side of the frequency filter resonator 17'in comparison to the exemplary embodiment in FIG. 2. In the exemplaryembodiment in FIG. 3, the two 4-GHz coaxial accesses of the frequencyfilters open directly into two coaxial waveguide junctions which areidentical to one another. The waveguide section, leading from left toright, of the front coaxial waveguide junction is such that it firstlyterminates at the intersection point of its longitudinal axis with theaxis of the corresponding, second waveguide section 18' which runsobliquely towards the front. Then this second waveguide section 18' hasthe same length as the corresponding, front waveguide section 18.Thereafter, the front waveguide section 18 is bent backwards in the formof a flattened E-bend by an easily compensatible angle, for example, of45° on its wide side, whereas the corresponding, other waveguide section18' which runs forward is bent to the right with the same E-bend. Inspite of the different directions of bend of the two E-bends in the twobranches of the line, these are precisely symmetrical to one another inrespect of construction. It should merely be ensured that the E₁₁interference fields of the probe coupling and of the adjacent E-bend areadequately decoupled from one another by an aperiodically attenuatingintermediate line.

In order to avoid a situation where the front radial circuit block 16 ispenetrated by the backwards bent waveguide 19, it is necessary to extendthis radial circuit block by a specific coaxial line section which canalso be employed, for example, as a plug connection. A further measurein order to avoid penetration of this kind consists in positioning thefront radial circuit block 16 not precisely in the center of thewaveguide wide side of the frequency filter resonator, but somewhatdisplaced towards the left. In order to ensure complete symmetry, theother radial circuit block 16' must then be displaced towards the frontby the same small quantity.

Thereafter the two lines 19 and 19' run symmetrically towards oneanother at double the angle of the individual E-bend, in the exemplaryembodiment illustrated in FIG. 3 at 90°, obliquely frontwards andobliquely backwards until the inner waveguide wide sides meet the anglebisector between the two lines. With the aid of two E-bends, againcompensated by slight flattening, of opposing direction over the widesides of the waveguide, the two 4-GHz connections 19, 19' are led intothe double waveguide of a 4-GHz wide wall coupler 20 which is formed bya rectangular pair of waveguides lying one upon another at their widesides, and the longitudinal axis of which is aligned at right angles tothe axis of the overall arrangement. The length of the waveguide doubleconnection which is designed to be fork-shaped and entirely symmetricalin construction amounts, in the exemplary embodiment, between the radialcircuit blocks and the 3-dB-coupler, to approximately one waveguide wavelength λ_(H).

The second double connection in the structure shown in FIG. 3 leadingfrom the 6-GHz-accesses of the frequency filters to a 6-GHz-3 dB-coupler20' is designed as follows. The double waveguide of the 6-GHz wide-wallcoupler 20', which is constructed in the same way as the 4-GHz wide-wallcoupler 20 and is likewise aligned with its longitudinal axis at rightangles to the main axis of the arrangement is connected to twocompensated 45° E-bends 21 which are identical to one another, thuswaveguide sections bent at the wide sides of the individual waveguides.For both arms there then follow two identical, compensated 90° H-bends22 which are executed over the waveguide narrow sides and whose startingaxes are aligned vertically upwards. Their starting cross-sections thuslie in a horizontal plane at right angles to one another and possess asymmetrical position to the angle bisector which is parallel to thecoupling axis. However, this position does not yet conform with theposition of the 6-GHz accesses 23 of the frequency filters, which, dueto the above described construction of the polarization filter, arearranged in a T-shape relative to one another. The parallel displacementof the cross-sections necessary for bridging purposes has been achievedin the exemplary embodiment with an oblique waveguide section 24. Theseoblique waveguide sections are of equal length to one another and cancommence directly following the frequency filter as phase- andreflection-compensated E-H double bend. In the above describedconstruction, the overall 6-GHz double line has a length which isapproximately equal to the length of one waveguide wave λ_(H) from thefrequency filters to the 3-dB-coupler.

The coupling of the wide-wall couplers shown in the exemplary embodimentin FIG. 3, is carried out via two rows of holes which run in parallelwith the edges of the common wall, with round individual openings 25.The arrangement illustrated in FIG. 3 is characterized by a particularlyshort structural length of approximately 330 mm in the 4/6 GHz design.On the other hand, in the radial direction, the extent is approximately660 mm along the horizontal. This radial dimension can advantageouslyfulfill a distributor function in respect of supplying two transmitterracks and two receiving amplifiers, and is frequently necessary in orderto spare further connection waveguides.

The aim of a further development of the invention is to employ a coaxial3-dB-coupler on the 4-GHz side instead of the waveguide couplerillustrated in the exemplary embodiment shown in FIG. 3, and toestablish the structurally symmetrical connection to the coaxial 4-GHzaccesses of the radio circuit blocks with the aid of coaxial lineelements. A fundamental reduction in the corresponding structural lengthis achieved by the use of short-slot couplers (one-hole couplers) in thetwo frequency ranges.

In a further development of the invention, the 6-GHz frequency filteraccesses are each connected to a 45° twisted component. Both twistedcomponents are then to be of identical construction, with the exceptionof the opposing direction of rotation. Then the two waveguidecross-sections at the rear of the twisted components are parallel to oneanother and laterally displaced from one another by a specific distance.A double waveguide which matches the wide-wall coupler here contains twodouble-bent, oblique waveguide sections which, apart from the directionsof bend, are identical to one another and therefore structurallysymmetrical. If the 6-GHz-coupler is connected here, when the remainderof the arrangement occupies the position shown in FIG. 3, it hangsvertically downwards. The length of this double line amounts toapproximately λ_(H).

The 6-GHz-coupler can also be pivoted out of a vertical position with aH-double bend into the horizontal plane. The length of a double-bentdouble line of this type amounts to approximately 1.5 λ_(H).

It should be noted that by interchanging the two 45° twisted componentsit is also possible to interchange the accesses for the right-hand andleft-hand circular polarization on the 6-GHz-3-dB-coupler, in which casethe coupler, in a vertical position, rotates 90° about its longitudinalaxis and, in a horizontal position, is rotated 90° in the horizontalplane.

A further development of the construction in accordance with theinvention combines the 4-GHz part of the arrangement illustrated in FIG.3, in which the waveguide coupler can be replaced by a coaxial coupler,with the 6-GHz part of the design of FIG. 2.

It will be apparent to those skilled in the art that many modificationsand variations may be effected without departing from the spirit andscope of the novel concepts of the present invention.

I claim as my invention:
 1. Antenna feed system for double polarizationin two high-frequency bands of different frequency position, consistingof a polarization shunt with a connecting flange in common on theantenna side for both frequency bands and two directional connectionsrespectively allocated to one polarization direction for a respectivefrequency shunt whose connection in common for said two frequency bandsis respectively connected to one of said directional connections of saidpolarization shunt, consisting of a first three decibel directionalcoupler for the lower frequency band whose double axis is respectivelyconnected to one further connection of both frequency shunts allocatedto the lower frequency band, and consisting of a three decibeldirectional coupler for said upper frequency band which is respectivelyconnected to one further connection of the frequency shunts allocated tosaid upper frequency band, characterized in that the polarization shuntis constructed phase-symmetrical with respect to its pass-through paths,in that the directional connections of said polarization shunt areconnected directly to the frequency shunts or respectively are connectedvia two 45° twisted pieces of different twisting direction which areprecisely constructionally symmetrical, and in that the connecting linesbetween said frequency shunts and said three decibel directionalcouplers for respectively two frequency bands of the same frequencyranges, said frequency bands existing in dual polarization directions,are constructed at the respectively same line location asphase-symmetrical line pairs with connection elements which coincide bypairs.
 2. Antenna feed system as claimed in claim 1, in which saidconnection lines between said frequency filters and said 3-dBdirectional couplers for in each case two frequency bands, occupyingdual polarization directions, of the same frequency range arestructurally symmetrical line pairs.
 3. Antenna feed system as claimedin claims 1 or 2, in which said polarization shunt is a symmetricallyconstructed, five-arm branching which contains a first arm which lies inthe longitudinal axis of the arrangement and is provided for theconnection of an ongoing waveguide of round or square cross-section, andfour sub-arms which are of similar design and of rectangularcross-section with a side ratio of at least approximately 1:2, which arearranged rotated by 90° relative to one another and run at the sameangle relative to the longitudinal axis of the arrangement and in theopposite direction to the first arm, and of which two of said sub-arms,lying opposite one another are connected via arm sections which areidentical to one another to the sub-arms of one of two series branchingsof similar design, two arm sections lying between opposite sub-arms ofsaid double branching and the sub-arms of said series branchings beingdesigned on the one hand as E-displacement components and on the otherhand as H-displacement components, said E-displacement components beingeach designed as straight rectangular waveguide components provided onboth sides with a waveguide elbow and bent on both sides by thewaveguide elbows in opposite directions along the waveguide wide side,the two E-displacement components, with their straight sections, beingaligned obliquely with respect to their narrow sides to the longitudinalaxis of the arrangement and run in parallel with one another, theH-displacement components each being designed as straight rectangularwaveguide components provided on both sides with a waveguide elbow andbent by the waveguide elbows on both sides in opposite directions alongthe waveguide narrow side, and one of said E-displacement componentsbeing accommodated between the H-displacement components in such amanner that the course of the series branchings connected to saidE-displacement components and said H-displacement components beingpenetration-free with respect to their sub-arms.
 4. Antenna feed systemas claimed in claim 2, in which said frequency filters each consist of afirst waveguide section in which both frequency bands exist, a secondwaveguide section which adjoins said first waveguide section and inwhich only said upper frequency band exists, said two waveguide sectionsbeing designed as rectangular waveguides of differing cross-sectionaldimensions, a radial circuit block having an extended inner conductorwhich blocks the upper frequency band is provided as output-couplingdevice, and the extended inner conductor leading through an opening inthe wall of said first waveguide section at a distance of approximatelyλ_(H) /4 from the effective short-circuit plane of the cross-sectionaljump occurring between said waveguide sections, where λ_(H) is assignedto a frequency contained in said lower frequency band.
 5. Antenna feedsystem as claimed in claim 4, in which said first waveguide section isconnected via a coupling opening to a third rectangular waveguidesection, and said radial circuit block being coupled to said thirdwaveguide section.
 6. Antenna feed system as claimed in claim 5, inwhich 3-dB directional couplers are designed as pairs of rectangularwaveguides arranged in an L-shape with respect to their cross-sectionalsurfaces, the narrow side of the one waveguide being located on the wideside of the other of said waveguide or possesses a common wall with apart of this wide side.
 7. Antenna feed system as claimed in claim 6, inwhich between the waveguides, coupling openings being provided which arecommon to both waveguides and which are located in the narrow waveguideside of the one waveguide and simultaneously in the edge zone of thewide waveguide side of the other of said waveguides.
 8. Antenna feedsystem as claimed in claim 7, in which at least two adjacent rows ofcoupling openings are provided.
 9. Antenna feed system as claimed inclaim 8, in which said coupling openings are in the form of longitudinalholes.
 10. Antenna feed system as claimed in claim 5, in which said3-dB-directional couplers are designed as pairs of rectangularwaveguides which are positioned one upon another on their wide sides.11. Antenna feed system as claimed in claim 10, in which the rectangularwaveguides of the 3-dB directional couplers possess a wide side designedas a common wall.
 12. Antenna feed system as claimed in claim 1, inwhich said connection lines between said frequency filters and said3-dB-directional couplers contain structurally symmetrical connectionelements, which match one another in pairs, at the same point of theline.
 13. Antenna feed system as claimed in claim 12, in whichrectangular waveguide sections aligned obliquely to the longitudinalaxis of the overall arrangement are provided as connection elementsbetween said 3-dB directional coupler provided for the higher-frequencyfrequency band and the rectangular terminals, assigned to the latter, ofthe frequency filters.
 14. Antenna feed system as claimed in claim 13,in which said 3-dB directional coupler provided for the lower frequencyband is directly coupled to the coaxial accesses of the said frequencyfilters.
 15. Antenna feed system as claimed in claim 10, in which said3-dB directional coupler provided for the lower frequency band isaligned with its longitudinal axis at right angles to the axis of saidpolarization shunt, and the coaxial accesses of said frequency filtersare connected structurally symmetrically to said 3-dB directionalcoupler provided for said lower frequency band in each case via acoaxial waveguide transition component and a waveguide connectioncomponent which is bent on both sides along said wide side.
 16. Antennafeed system as claimed in claim 10, in which said 3-dB directionalcoupler provided for said upper frequency band is aligned with itslongitudinal axis at right angles to the axis of said polarization shuntand is connected to two compensated, 45°-E-bend elements which areidentical to one another, the 45°-E-bend elements being connected tocompensated H-bend elements which are identical to one another and whoseoutput axes are aligned parallel to the longitudinal axis of saidorthomode transducer, and that between siad H-bend elements and saidterminals, provided for said upper frequency band, of said frequencyfilters there are arranged further, oblique waveguide sections which areidentical to one another.
 17. Antenna feed system as claimed in claim10, in which between the outputs, assigned to said upper frequency band,of said two frequency filters and the double access of the 3-dBdirectional coupler provided for the upper frequency band there arearranged two exactly structurally symmetrical 45°-twisted components ofdiffering twisting direction, and two adjoining, oblique, straight linecomponents which are structurally symmetrical to one another. 18.Antenna feed system as claimed in claim 3, in which said frequencyfilters each consist of a first waveguide section in which bothfrequency bands exist, a second waveguide section which adjoins saidfirst waveguide section and in which only said upper frequency bandexists, said two waveguide sections being designed as rectangularwaveguides of differing cross-sectional dimensions, a radial circuitblock having an extended inner conductor which blocks the upperfrequency band is provided as output-coupling device, and the extendedinner conductor leading through an opening in the wall of said firstwaveguide section at a distance of approximately λ_(H) /4 from theeffective short-circuit plane of the cross-sectional jump occurringbetween said waveguide sections, where λ_(H) is assigned to a frequencycontained in said lower frequency band.
 19. An antenna feed system fordouble polarization in two respective high-frequency bands of differentfrequency position, consisting of a polarization shunt (PW) with aconnecting flange (1) in common on the antenna side for both frequencybands and two directional connections (SV) (see FIG. 4) respectivelyallocated to one polarization direction for a respective frequency shunt(FW) whose connection (=SV) in common for the two frequency bands isrespectively connected to one of the directional connections (SV) of thepolarization shunt (PW), consisting of a first three decibel directionalcoupler (RK2) (FIG. 2) for the lower frequency band whose double axis isrespectively connected to one further connection of both frequencyshunts (FW) allocated to the lower frequency band, and consisting of athree decibel directional coupler (RK1) for the upper frequency bandwhich is respectively connected to one further connection of thefrequency shunts (FW) allocated to the upper frequency bandcharacterized in that the polarization shunt (PW) is constructedphase-symmetrical with respect to its pass-through paths, in that thedirectional connections (SV) of the polarization shunt are connecteddirectly to the frequency shunts (FW) or respectively are connected viatwo 45° twisted pieces of different twisting direction which areprecisely constructionally symmetrical, and in that the connecting linesbetween the frequency shunts (FW) and the three decibel directionalcouplers (RK1, RK2, 20, 20') for respectively two frequency bands of thesame frequency range, said frequency bands existing in dual polarizationdirections, are constructed at the respectively same line location asphase-symmetrical line pairs with connection elements which coincide bypairs.
 20. Antenna feed system for double polarization in twohigh-frequency bands of differing frequency position, comprising apolarization shunt with a connection in common on the antenna side forboth frequency bands and two directional connections respectivelyallocated to one polarization direction for a respective frequencyshunt, two frequency filters whose connection is common to said twofrequency bands, is in each case connected to one of said directionalconnections of said polarization shunt, a first 3-dB directional couplerfor the lower of said frequency bands whose double access is in eachcase connected to a further terminal, assigned to the lower frequencyband of said two frequency filters, and further consisting of a 3-dBdirectional coupler for said upper frequency band which is connected toa further terminal, assigned to said upper frequency band of saidfrequency filters, said polarization shunt being constructed to bephase-symmetrical with respect to its transit paths, the directionalterminals of said polarization shunt being connected directly or via twoexactly structurally symmetrical 45° twisted components of differingtwisting direction, to said frequency filters, said connection linesbetween said frequency filters and said 3-dB directional couplers ineach case for said two frequency bands, occupying dual polarizationdirections of the same frequency range, are constructed asphase-symmetrical pairs of lines with connection elements which matchone another in pairs at the same point of said line.